Banner3

Rosliston Astronomy Group

Astrophotography

Click here to return to RAG home page

If you can’t see flash navigation box below, text links are at bottom of page

NGC891 & M33

26/8/2014

Roger Samworth

 

An interesting experiment is to set your camera to manual aperture and see what difference 1 aperture stop makes - not as lot! After all going from 8" to 12" is only 1 stop, going from 10" to 12" is les than half a stop -you can hardly see that with a camera. I used to have a rule of thumb that if you up-aperture you need to go 2 stops, hence years ago I went from 4" to 8". It is more about contrast, and as you say, in our skies, the sky-glow limits that. The same thing applies to image intensifiers - they don't increase contrast, which is what you want.

I know! I know! I recently bought a 12" newt which is only 1 stop up on my 8" SCT - but that was more along the lines of not being able to resist a bargain, and wanting a simple dob!

You do gain a bit with aperture as you can increase magnification for the same contrast but it isn't much.

You CAN increase contrast to a certain extent by taking pics and doing a bit of image processing with GIMP say. For example take a look at the pictures of NGC891 and M33 below that I recently took with my PD camera. These were only a few 20-sec exposure frames stacked - but then processed with GIMP. I have always had difficulty even seeing these with the old eyeball!

Roger

 

M33

8-23-14 m33dssb

NGC891

8-23-14 ngc891dssc
[Photos/Drawings] [Techniques & Tips] [Pluto Time] [Photographs, drawiings and video by members of RAG after April 2014] [Andy Mac] [Andrew Thornett] [Chris Howe] [Damian] [Dave Jones] [Ed Mann] [Geoff Dryland] [Julian Palmer] [Kenneth Crichton] [Lewis Brailsford] [Nick Cox] [Paul Bertenshaw] [Peter Hill] [Rachel & David Donaldson] [Roger Samworth]